UnrealEngineUWP/Engine/Shaders/PostProcessBloom.usf

// Copyright 1998-2014 Epic Games, Inc. All Rights Reserved.

/*=============================================================================
	PostProcessBloom.usf: PostProcessing bloom
=============================================================================*/

#include "Common.usf"
#include "PostProcessCommon.usf"

// vertex shader entry point
void MainPostprocessCommonVS(
	in float4 InPosition : ATTRIBUTE0,
	in float2 InTexCoord : ATTRIBUTE1,
	out float4 OutTexCoord : TEXCOORD0,
	out float4 OutPosition : SV_POSITION
	)
{
	DrawRectangle(InPosition, InTexCoord, OutPosition, OutTexCoord.xy);
	OutTexCoord.zw =  OutPosition.xy;
}

// vertex shader entry point
void MainVS(
	in float4 InPosition : ATTRIBUTE0,
	in float2 InTexCoord : ATTRIBUTE1,
	out float4 OutTexCoord : TEXCOORD0,
	out float OutExposureScale : TEXCOORD1,
	out float4 OutPosition : SV_POSITION
	)
{
	MainPostprocessCommonVS(InPosition, InTexCoord, OutTexCoord, OutPosition);

#if FEATURE_LEVEL >= FEATURE_LEVEL_SM5
	// texture can be GWhiteTexture which is 1x1. It's important we don't read outside bounds.
	OutExposureScale = EyeAdaptation.Load(int3(0, 0, 0)).r;
#else
	OutExposureScale = 1;
#endif
}

// x:BloomThreshold, yz:unused, w:ExposureScale (useful if eyeadaptation is locked)
float4 BloomThreshold;
// -----------------------------
// bloom threshold
void MainPS(
	  float4 UVAndScreenPos : TEXCOORD0
	, float InExposureScale : TEXCOORD1
	, out float4 OutColor : SV_Target0)
{
	float2 UV = UVAndScreenPos.xy;

	half4 SceneColor = Texture2DSample(PostprocessInput0, PostprocessInput0Sampler, UV);

	// clamp to avoid artifacts from exceeding fp16 through framebuffer blending of multiple very bright lights
	SceneColor.rgb = min(float3(256 * 256, 256 * 256, 256 * 256), SceneColor.rgb);
	
	half3 LinearColor = SceneColor.rgb;

	float ExposureScale = InExposureScale;

#if NO_EYEADAPTATION_EXPOSURE_FIX 
	ExposureScale = BloomThreshold.w;
#endif

	// todo: make this adjustable (e.g. LUT)
	half TotalLuminance = Luminance( LinearColor ) * ExposureScale;
	half BloomLuminance = TotalLuminance - BloomThreshold.x;
	// mask 0..1
	half BloomAmount = saturate(BloomLuminance / 2.0f);

	OutColor = float4(BloomAmount * LinearColor, 0);
}